Deprecate api.VolunteerUtil.getbeneficiaries

api.VolunteerUtil.getbeneficiaries is a workaround for the lack of a getList function that returns human-readable data for the VolunteerProjectContact entity. A bona fide getList function would have more utility (e.g., produce a list of volunteer managers).

The getbeneficiaries action is used only once in the application, but we have additional need for it in near future. Now is the time to replace it before it becomes too entrenched.